Thermoplastic composite composition reinforced with mica and wooden fiber filler

ABSTRACT

A thermoplastic resinous composite material has the good flowability of a meltage of the composite material during a molding process and can provide not only the excellent tensile strength, the excellent flexural strength, the excellent flexural elasticity and the excellent H.D.T of a product molded using the composite material but also provide the better impact resistance which can not be achieved by a composite material of the art. The thermoplastic resinous composite material is made from a mixture mainly consisting of mica, a wood cellulose filler and a thermoplastic resin. The mix proportion of mica, the wood cellulose filler and the thermoplastic resin is 10-50 weight by parts 10-43 weight by parts: 70-82 weight by parts.

TECHNICAL FIELD

The present invention relates to a thermoplastic resinous compositematerial used for a variety of molding processes, and, in particular,relates to a thermoplastic resinous composite material made from amixture consisting of a certain size of a flat inorganic material, awood cellulose filler, and a thermoplastic resin in a predetermined mixproportion, so as to provide the good flowability of a meltage of thecomposite material during a variety of molding processes and provide notonly the excellent tensile strength, the excellent flexural strength,the excellent flexural elasticity and the excellent heat deformationtemperature (hereinafter written as H.D.T) but also the good impactresistance of a product molded using the composite material.

BACKGROUND OF ART

A thermoplastic resinous composite material is molded into panel boardsand parts by a molding technique such as an extrusion molding and aninjection molding. Talc or calcium carbonate may be used as an additivematerial to be contained in the composite material in order to improvethe physical property of a product molded using the composite material.Mica is also widely used as such an additive material.

In general, the shape of mica is flat, and it is known that mica is welldispersed in a meltage of the composite material during a moldingprocess and is orientated along a surface of a product molded using thecomposite material (see FIG. 2) and is also known that the product madefrom the composite material containing mica is excellent in the tensilestrength, the flexural strength, the flexural elasticity and the H.D.T.Thus, less than 800 μm in weight average flake size and 30-50 in weightaverage aspect ratio of mica is contained in the thermoplastic resinouscomposite material.

Also, it is well known that a composite material made from a mixture ofpolypropylene and a wood cellulose filler, such as a wood powder and apaper, is used for an extrusion molding.

The wood cellulose filler mixed is obtained by grinding a wood materialin about 40-200 mesh. This wood cellulose filler contains large a largequantity of cylindrical fragments and a small quantity of granulousfragments, as shown in FIG. 1 (FIG. 1 is a rough sketch of a wood powdermagnified by a microscope).

In a molding process which uses a composite material made from a mixtureof such a wood cellulose filler and an olefin series plastic, the woodcellulose filler is strongly orientated in a flow direction (i.e. ameltage of the composite material is flowing in the flow direction andis simultaneously molded) so as to cause differences in magnitude of thetensile strength, the flexural strength, the flexural elasticity and theimpact resistance between the flow direction and a directionperpendicular to the flow direction, so that a product molded using sucha composite material is warped and distorted.

In addition, the tensile strength and the flexural elasticity of theproduct are excellent in the flow direction, because the wood cellulosefiller is strongly orientated in the flow direction. However, if theamount of the wood cellulose filler added is increased, the fragility ofthe product is increased i.e. the impact resistance thereof isconsiderably reduced.

In addition, the shape of each fragment of the ground wood cellulosefiller is uneven and the surface thereof has irregularities so as toeasily hitch. However, if the wood cellulose filler is mixed togetherwith the olefin series plastic having a smooth surface, fragments of thewood cellulose filler and particles of the olefin series plastic areseparated from each other by vibrations caused when the mixture isfalling down from a hopper (located at a section for supplying thecomposite material to a molding machine) to a screw section, so that themix proportion is changed.

In addition, while the wood cellulose filler is melted and mixedtogether with the olefin series plastic in the screw section, the woodcellulose filler is not well dispersed in a meltage of the compositematerial in comparison with inorganic fillers. Thus, if a compositematerial containing such a wood cellulose filler is used, the physicalproperty to be exhibited in each product molded may be different and isoften largely differed.

As discussed above, the additive material and the filler are veryeffective materials for improving the physical property of the productsuch as the tensile strength, the flexural strength, the flexuralelasticity and the H.D.T. However, the good impact resistance of theproduct can not be achieved in simultaneous with those physicalproperties.

Several methods have been provided for achieving the good impactresistance in simultaneous with achieving the good tensile strength, thegood flexural elasticity and the good H.D.T.

For example, there is a method which improves the impact resistance byundergoing a rubber-modification process to modify the olefin seriesplastic into ethylene-modified-polypropylene in a composite materialmade from a mixture consisting of the olefin series plastic and aninorganic material such as talc, calcium carbonate and the like.However, in this method, the flowability of a meltage of the compositematerial during a molding process is reduced and the cost is essentiallyhigh so that this method is not practical.

In European Patent No. 0319589 (corresponding to Japanese PatentPublication No. Showa 60(1985)-40965 entitled “Method and Apparatus forproducing Panel”), in a composite material made from a mixture mainlyconsisting of a wood cellulose filler such as a wood powder and anolefin series plastic, fiber flax is used in combination therewith. Inthis method, the impact resistance to be achieved in a product moldedusing the composite material is excellent. However, the flexuralelasticity of the product and the flowability of a meltage of thecomposite material during a molding process are considerably reduced.

In addition, in Japanese Patent Publication No. Showa57(1982)-43575entitled “Composite Material using Paper and Method forproducing same”, in a composite material made from a mixture mainlyconsisting of a wood cellulose filler such as a paper and an olefinseries plastic, a natural or synthetic rubber is used in combinationtherewith. In this method, the impact resistance is improved byelastomer. However, the cost is high, the flowability of a meltage ofthe composite material during a molding process is considerably low, andthe productivity is low.

As discussed above, in a composite material made from a mixture of anolefin series plastic and an inorganic filler such as talc or an organicfiller such as a wood cellulose, the physical property exhibited in aproduct molded using the composite material is excellent in the tensilestrength, the flexural strength, the flexural elasticity and the H.D.T,and such excellent properties can be easily provided for the product bycontrolling the amount and the size of the filler to be added. However,the impact resistance of the product is reduced. In other words, asimproving the impact resistance, not only the physical property such asflexural elasticity and the like but also the flowability of a meltageof the composite material during a molding process are considerablyreduced.

This is because the physical property such as the tensile strength, theflexural elasticity and the H.D.T is, in general, contrary to the impactresistance of the product and the flowability of the composite materialduring a molding process.

Thus, it has been believed that it is difficult to provide athermoplastic resinous composite material which has the good flowabilityof a meltage of the composite material during the molding process andwhich can provide the good flexural strength, the good flexuralelasticity, and the good H.D.T for a product molded using the compositematerial and can also achieve the good impact resistance.

The present invention is made in view of those matters discussed above.An object of the present invention is to provide a thermoplasticresinous composite material which has the good flowability of a meltageof the composite material during the molding process and which canprovide the good flexural strength, the good flexural elasticity, andthe good H.D.T for a product molded using the composite material and canalso achieve the good impact resistance which can not be achieved by acomposite material of the art.

Another object of the present invention is to provide the abovecomposite material suitable for use in an extrusion molding, acompression molding, a transfer molding and a blow molding.

Still another object of the present invention is to provide the abovecomposite material usable for an injection molding.

DISCLOSURE OF THE INVENTION

A thermoplastic resinous composite material of the present invention ismade from a mixture mainly consisting of mica, a wood cellulose fillerand a granulous thermoplastic resin which are evenly dispersed therein.

The mix proportion of mica, the wood cellulose filler and thethermoplastic resin is 10-50 weight by parts: 10-43 weight by parts:70-82 weight by parts.

If the thermoplastic resinous composite material is used in an extrusionmolding or a blow molding, it is desirable that the mix proportion ofmica, the wood cellulose filler and the thermoplastic resin is 10-35weight by parts: 10-30 weight by parts: 50 weight by parts. If thethermoplastic resinous composite material is used in an injectionmolding, it is desirable that the mix proportion of mica, the woodcellulose filler and the thermoplastic resin is 15-35 weight by parts10-25 weight by parts: 65 weight by parts.

The kind and the shape of the wood cellulose filler are not strictlylimited and are determined depending on a purpose of use. The woodcellulose filler is preferably selected from wood powders obtained bygrinding a wood material such as a needle-leaf tree, a broad-leaf tree,a hard board and the like. The wood powder is various in shape and maybe ground in granulous, laminar or the other shapes. The size of thewood powder is not strictly limited, but if the size is too large, thewood powder will come up to a surface of a product molded, so that sucha large size of the wood powder affects the visual quality of theproduct and causes an internal stress in the product so as to reduce thephysical property thereof. If the size of the wood powder is too small,the dispersibility will be reduced so as to make worse the flowabilityof a meltage of the composite material during a molding process and tomake worse the physical property (in particular, the impact resistance).Thus, it is desirable that the size of the wood powder is 50-700 μm.When the composite material is used in an extrusion molding or a blowmolding, it is desirable that the size of the wood powder is 70-600 μmand the water content thereof is 2%. When the composite material is usedin an injection molding, it is desirable that the size of the woodpowder is 70-300 μm and the water content is 2%.

Mica used herein is an important component of the composite material ofthe present invention, and the weight average flake size and the weightaverage aspect ratio thereof is a basis for achieving the effect of thepresent invention.

Some of composite materials of the art are made from a mixture of micaand an olefin series plastic. In a product molded using the compositematerial of the art, micaceous flakes are strongly orientated on asurface portion of the product (see FIG. 2) so as to provide the goodphysical property in a flow direction of a meltage of the compositematerial during a molding process and in a direction perpendicular tothe flow direction (in two directions). Thus, the inventors of thepresent invention have studied whether the reduction of the impactresistance caused by the wood cellulose filler can be restrained or not.However, even though mica having the same size as mica used in thecomposite material of the art composed of mica and an olefin seriesplastic is merely contained in a composite material composed of a woodcellulose filler and an olefin series plastic, the impact resistance cannot be improved, rather is reduced by increasing the amount of such anadditive material to be contained in the composite material.

Thus, the inventors of the present invention have conducted a variety oftests and researches and have then found that it is necessary to matchthe size of mica to the size of the wood cellulose filler (i.e. the sizeof mica used in the present invention is larger than that of the art) sothat the orientation of mica becomes the same as or slightly larger thanthe orientation of the wood cellulose filler.

The weight average flake size of mica is preferably 100-300 μm, morepreferably 200-280 μm. The aspect ratio of mica is preferably 50-75,more preferably 60-70.

The good impact resistance can be provided for a product molded using acomposite material made from a mixture containing such mica. Inaddition, such a size of mica can accelerate the dispersibility of thewood cellulose filler and matches to the size of the cylindrical woodcellulose filler, and mica is evenly mixed with the filler so as toserve as a lubricant, so that the flowability of a meltage of thecomposite material containing the wood cellulose filler and athermoplastic resin is improved. Thus, the thermoplastic resinouscomposite material of the present invention is usable not only for anextrusion molding and a compression molding but also for an injectionmolding and a blow molding.

In addition, when dry mixing and stirring such mica with the woodcellulose filler and the thermoplastic resin and dropping this mixturefrom a hopper (for introducing to a molding machine) to a screw sectionand when melting and kneading it in the screw section, the mixproportion of mica, the wood cellulose filler and the thermoplasticresin does not change, so that those components are evenly mixedtogether in most efficient.

It is desirable that the thermoplastic resin used in the presentinvention is an olefin series plastic desirably selected from the groupconsisting of polyethylene, polypropylene, and a modified or inducedcompound thereof.

The mix proportion of mica, the wood cellulose filler and thethermoplastic resin is as discussed above. Such a mix proportion hasbeen determined on the basis of a variety of conditions discussed aboveso that the good flowability of a meltage of the composite materialduring a molding process and the good impact resistance which can not beachieved by a composite material of the art can be achieved insimultaneous with the good tensile strength, the good flexural strength,the good flexural elasticity and the good H.D.T of a product moldedusing the composite material.

The physical property as described above can be achieved. This isbecause a predetermined size of mica, the wood cellulose filler and thethermoplastic resin are mixed together. Also, there may be the followingreason as the other reasons why such a physical property can beachieved. That is, even though the wood cellulose filler to be containedin the composite material is dried at high temperature, when the woodcellulose filler is heated with the other components of the compositematerial at 190−230° C., the residual free water is oozed out on asurface thereof and it exhibits acid. Such oozed out free water inhibitsthe adhesion to the thermoplastic resin (i.e. the olefin seriesplastic), but when mica and the free water at this temperature arecontacted each other, it exhibits alkaline so as to neutralize saidacid, so that the inhibitor on the contact surface between the woodcellulose filler and the olefin series plastic is inactivated so as topromote the adhesion therebetween. As a result, the good and balancedphysical property can be provided by a combination of mica and the woodcellulose filler.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a magnified rough sketch of a wood cellulose filler (a woodpowder) mixed in a composite material.

FIG. 2a is a perspective view of a product molded using a compositematerial of the present invention by an injection molding and theproduct is shown with a flow direction of a meltage of the compositematerial during the molding process, and

FIG. 2b shows cross sectional views of (A) and (B) of FIG. 2a.

BEST MODE FOR CARRYING OUT THE INVENTION

Using a thermoplastic resinous composite material according to thepresent invention, two products are molded. One is produced by anextrusion molding, and the other is produced by an injection molding.Table 1 shows the physical property of each product.

The mix proportion of components of the composite material used for theproduct molded by the extrusion molding is 50 weight by parts(polypropylene): 15-35 weight by parts (mica): 10-30 weight by parts (awood powder). The mix proportion of components of a composite materialused for the product molded by the injection molding is 65 weight byparts (polypropylene): 10-35 weight by parts (mica): 5 10-20 weight byparts (a wood powder).

TABLE 1 Product Product (by Extrusion) (by Injection) Flowability (MFR)3.0-5.5 9.5-7   Density (g/cc) 1.07-1.14 1.07-1.13 Tensile Strength(kg/cm²) 320-380 320-345 Flexural Elasticity (kg/cm²) 32000-4500022000-35000 Impact Resistance (IZOD notch) 2.5-3.4 3.1-3.7 (kg cm/cm)H.D.T. (186 kg/cm³ ° C.)  97-112  97-107

FIG. 2a is a perspective view of a product molded using the compositematerial. The product is shown with a flow direction of a meltage of thecomposite material during the molding process. FIG. 2b shows crosssectional views which show the aspects of orientations in the flowdirection and a direction perpendicular to the flow direction,respectively. Those cross sectional views are depicted on the basis ofphotographs of those cross sections. As shown, micaceous flakes and thewood cellulose filler are strongly orientated in two directions on asurface of the product.

As described above, a thermoplastic resinous composite materialaccording to the present invention, which contains a wood cellulosefiller and mica whose size matches to the size of the wood cellulosefiller in a predetermined mix proportion, advantageously provides a goodimpact resistance and a good flowability of a meltage of the compositematerial during a variety of molding processes which can not be achievedby the art in simultaneous with an excellent tensile strength, anexcellent flexural strength, an excellent flexural elasticity and anexcellent H.D.T, for a product molded using the composite material.

In a composite material of the art, the flowability of a meltage of thecomposite material during a molding process is not sufficient forproviding a good impact resistance for a product molded using thecomposite material, and thus, the composite material of the art composedof an olefin series plastic and a wood cellulose filler such as woodpowder and a paper can not be used for an injection molding. Such aproblem of the art is advantageously overcome by the composite materialof the present invention, and the composite material of the presentinvention is usable not only for an extrusion molding and a blow moldingbut also for an injection molding under common conditions, and as aresult, the application of the composite material is expanded.

In general, as a problem of a composite material containing a woodcellulose filler, each product molded using the composite material mayhave a variety of strength and may be warped and distorted. Thecomposite material of the present invention considerably restrain such avariety of strength, warping and distortion.

It is not necessary to provide a special grade of microscopically groundmica as mica added in the composite material of the present invention,and thus, the composite material can be provided in a relatively lowcost.

What is claimed is:
 1. A thermoplastic resinous composite material madefrom a mixture mainly consisting of mica, a wood cellulose filler, and agranulous thermoplastic resin, characterized in that: 10-50 weight byparts of mica, 10-43 weight by parts of the wood cellulose filler, and70-82 weight by parts of the thermoplastic resin, are evenly dispersedtherein, and the weight average flake size of said mica is 100-300 μm,the aspect ratio of said mica is 60-70, and said wood cellulose filleris a powder that has a size of 70-300 μm, and a water content of lessthan 2%.
 2. The thermoplastic resinous composite material of claim 1,wherein 10-35 weight by parts of mica, 10-30 weight by parts of the woodcellulose filler, and 50 weight by parts of the thermoplastic resin, areevenly dispersed therein, when said thermoplastic resinous compositematerial is used for an extrusion molding or a blow molding.
 3. Thethermoplastic resinous composite material of claim 1, wherein 10-35weight by parts of mica, 10-25 weight by parts of the wood cellulosefiller, and 60 weight by parts of the thermoplastic resin, are evenlydispersed therein, when said thermoplastic resinous composite materialis used for an injection molding.
 4. The thermoplastic resinouscomposite material of claim 1, wherein the weight average flake size ofsaid mica is 100-280 μm, and the aspect ratio thereof is 60-70.
 5. Thethermoplastic resinous composite material of claim 1, wherein saidthermoplastic resin is an olefin series plastic.
 6. The thermoplasticresinous composite material of claim 4, wherein the weight average flakesize of said mica is 100-280 μm, and the aspect ratio thereof is 60-70.7. A thermoplastic resinous composite comprising: 10-50 parts by weightmica, where said mica has a weight average flake size of 100-300 μm;10-43 parts by weight wood cellulose filler, where said wood cellulosefiller has a size that is 70-300 μm; and 70-82 parts by weightthermoplastic resin.
 8. The thennoplastic resinous composite material ofclaim 7, where the composite comprises 10-35 parts by weight of saidmica, 10-30 parts by weight of said wood cellulose filler, and 50 partsby weight of said thermoplastic resin.
 9. The thermoplastic resinouscomposite material of claim 7, where said composite comprises 15-35parts by weight of said mica, 10-25 parts by weight of said woodcellulose filler, and 65 parts by weight of said thermoplastic resin.10. The thermoplastic resinous composite material of claim 7, where saidwood cellulose filler has a water content of less than 2%.
 11. Thethermoplastic resinous composite material of claim 7, where the weightaverage flake size of said mica is 100-280 μm.
 12. The thermoplasticresinous composite material of claim 11, where the weight average flakesize of said mica is 200-280 μm.
 13. The thermoplastic resinouscomposite material of claim 7, where the aspect ratio of said mica is50-75.
 14. The thermoplastic resinous composite material of claim 13,where the aspect ration of said mica is 60-70.
 15. The thermoplasticresinous composite material of claim 7, where said thermoplastic resinis polyethylene, polypropylene, or a modified or induced compoundthereof.
 16. A thermoplastic resinous composite comprising: 10-50 partsby weight mica, where said mica has a weight average flake size of100-300 μm and an aspect ration of 50-70 10-43 parts by weight woodcellulose filler, where said wood cellulose filler has a size that is70-300 μm and a water content that is less than 2%; and 70-82 parts byweight of polyethylene, polypropylene, or a modified or induced compoundthereof.